Large aquatic electrical barriers are installed for various purposes related to aquatic species management, especially in the field of non-native species management. The goal is to protect the habitats or microhabitats from the effects of non-native species.
Aquatic electrical barriers are deployed in two general scenarios: the first is for the prevention of fish passage from one location to another, and the second is for inducing fish to move from one locality to another. In the first scenario, an electrical field is used to prevent fish from moving between two locations: from a river or stream to a lake, from a river or stream to an irrigation canal, from a river to a hydroelectric facility intake, or from migrating upstream that would avoid entry into a fish hatchery. In the second scenario, an electrical field is used to guide fish: to induce fish movement out of a navigation lock to insure that it is devoid of fish before the entry of a boat into that lock. In both scenarios, the electrical field is used as a mechanism the movement of invasive and/or native species.
Aquatic electrical barriers pass an electrical current through a body of water which, in turn, causes a physiological reaction by the aquatic species. A terrestrial analog to aquatic barriers is the “electric fence”. Both aquatic barriers and electric fences use electric current to cause a deterrent effect. But since aquatic species are immersed in a conductive liquid, (e.g. water), the gradient electric field is continuous as opposed to the contact imposed field of the electric fence. This gradient field is caused by placing a conductive anode and cathode in the water and by passing a current between the conductors.
The physiological reactions of an aquatic species that is affected by an aquatic barrier are typically categorized as repulsion, narcosis (“stunning”), and euthanasia (“death”).
The aforementioned physiological responses generally correlate to the is amount of electrical power that is transferred from the water to the aquatic species. The electrical power transfer occurs as a result of the body of the fish acting as a “voltage divider” in the water. The total amount of energy that is transferred from the water to the aquatic species is calculated by measuring the potential difference across the fish, multiplied by the duty cycle of the pulse, and which is then multiplied by the electrical current that passes through the fish.
Large waterways typically have a barrier system that consists of several electrical barriers that are separated by distances ranging from approximately 200 to 1500 feet. The DC pulse generators that are installed at these barriers are powered by high voltage supplies (“pulsators”) that are connected to the commercial electrical grids. A representative example of such a barrier system is located in the Chicago Sanitary and Ship Canal, where the width of the canal is 160 ft, the depth of the canal is approximately 25 ft, and the conductivity of the water general does not usually exceed 3500 micro Siemens. In this barrier system, a single pulsator has high power output which can reach 1,500 kW.
In large electric fish barrier systems, the use of multiple pulsators are configured to create a series of physically separate electric fields that improve's the deterrence of fish. The barrier system's use of multiple pulsators is also necessary in the event of the failure of one pulsator. Therefore, operating multiple pulsators, that are located physically in series on a waterway, can more effectively prevent is the upstream and/or downstream migration of fish by reducing or screening the number of fish as the water flows through each successive barrier.
Pulsators in a fish barrier system can operate individually (un-synchronized) but are almost always connected to a common electrical grid. While each pulsator in the barrier may be outputting pulses at a fixed frequency, the individual pulses from one pulsator occur are unsynchronized with respect to the pulses from other pulsators in the installation. It is also not uncommon for the individual pulses to slowly drift in time with respect to each other. This results in repetitive periods of time where the pulses occur at unique points in time and later can be seen to be partially or fully temporally overlapped with each other. Overlapping pulses of individual pulsators in an electrical barrier system is undesirable.
There are at least three situations where the unsynchronized operation of multiple pulsators is undesirable:                1) Where there is a navigation lock in the waterway, there is a need to synchronize the energized pairs of bottom mounted electrodes. The objective is to simultaneously expose the fish to physically undesirable (electrified) zones and more desirable (non-electrified) zones that provide the fish with an avenue of escape. In this configuration, it is essential that the individual pulsators connected to the electrodes are synchronized.        2) When high-power pulsators are utilized, there is the possibility that the pulsators cause electrical disturbances that are fed back into the AC power line. AC “line notching” is an example of such a disturbance and is characterized by a sudden, short duration, drop in voltage during a portion of the AC line sine wave. The magnitude of the line notching increases when the output from two (or more) pulsators occur at the same point in time. If the output of the pulsators can be synchronized so that their output pulses occur at unique time “slots” or “windows” then the peak amplitude of line notching can be minimized.        3) The electrodes of electric fish barrier typically do not rest on a perfectly electrically insulating substrate. A small percentage of pulsator current will flow through the substrate and into the rock/earth locally surrounding the in-water electrodes. When the pulses of geographically separate pulsators temporally overlap, a stray electrical current may be induced between the substrates that increases the probability of an interference with adjacent electronic signaling systems.        
As noted, during operation, these large pulsators can create localized potential disturbances consisting of, but not limited to: ground loops, line notching, harmonic distortion, and an excessive power factor (collectively “local electrical disturbances”). These local electrical disturbances can also introduce signal noise into local conductors. These local conductors include, but are not limited to local railroad signaling lines which are used for controlling railroad devices, such as cross arms. Signal noise, on these railroad signal lines, can cause local transmission errors which results in operational malfunctions. Although these operational malfunctions (typically cross arms being deployed when a train is not in the proximity) are an inconvenience and are costly for those individuals affected by the malfunction and for the companies must service these types of malfunctions.
The conventional solution to pulsator de-synchronization is to use interconnecting synchronization wires. Wires are susceptible to damage and are expensive to install. It is not uncommon for buried cables to be disturbed and/or broken by earth moving activities such as road building, trenching, general construction, etc.
Although there is prior art that describes the use of GPS to synchronize electrical equipment, for example, U.S. Pat. No. 8,044,855 to Hanabusa on Oct. 25, 2011. But the '855 patent does not describe apparatus and methods for wireless electrical barrier system pulsator desychronization. U.S. Pat. No. 7,333,725 issued to Frazier on Feb. 19, 2008 describes a system for the synchronization of sensors, but this printed publication fails to describe or illustrate how synchronize multiple barriers would operate within an electric barrier system.
Although electrical currents affect all aquatic species, the term “fish” is used in this application to be synonymous with aquatic species and is not to limit the scope of this term.
Therefore, what is needed is a solution that provides for an improved aquatic barrier system that provides for electrical pulse desynchronization between individual pulsators.